Spleen: Imaging Approach and Differential Diagnosis

Embryology , Anatomy , and Physiology

The spleen develops from the dorsal mesogastrium and usually rotates to the left, becoming fixed in the left subphrenic location by peritoneal reflections linking it to the diaphragm, abdominal wall, stomach (gastrosplenic ligament), and kidney (splenorenal ligament). It usually develops as 1 "fused" mass of tissue, but variations are common.

One or more accessory spleens are found in up to 30% of the general population, usually small spherical structures near the splenic hilum. These can enlarge, especially following splenectomy, and may simulate a neoplastic mass or cause recurrence of hematologic disease.

The spleen may be congenitally absent ( asplenia ) or have many unfused components ( polysplenia ). These are rare splenic anomalies and are associated with cardiovascular anomalies, situs inversus, and other anomalies, often with serious and even life-threatening consequences.

The spleen is rarely on a long mesentery and may be found in any abdominal or pelvic location ("wandering spleen"), placing it at risk for trauma and torsion with infarction.

The spleen is the largest lymphatic organ, the size of which varies among individuals and even in the same person by blood volume, state of nutrition, and hydration. The usual volume range is 100-250 cm³ with a mean of 150 cm³. A calculated splenic index (length x width x breadth) over 480 cm³ is considered splenomegaly. The average length is up to 12 cm with a width and breadth of 7 and 4 cm, respectively.